The present invention relates generally to porous implants, and more particularly, to a new and improved porous implant and method for making same, wherein a biodegradable material is placed within the pores of the porous coating of the implant to hinder the migration of wear particles into these pores, thus aiding in the prevention of osteolysis at the implant site.
The use of various prosthetic implant systems, such as those used for the total replacement of knees and hips, has become increasingly more commonplace. For example, hip replacements are performed to alleviate conditions caused by osteoarthritis, rheumatoid arthritis, fractures, dislocations, congenital deformities, and other hip-related conditions.
Total hip arthroplasty involves replacing the damaged surfaces of the hip with artificial surfaces. Typically, the surgeon removes the head and neck of the femur and replaces them with a femoral component comprised of a metallic ball and stem. The damaged hip socket is lined with an acetabular component which is typically comprised of a metallic cup lined with a plastic material (such as polyethylene). The ball and stem fit into this cup, creating a new, movable hip joint.
Before 1983, most hip replacements in the United States were done using acrylic-based cements (e.g., polymethylmethacrylate) to attach the prosthetic components to the respective portions of the femur and pelvis of the patient. The area between the metal implant and the surrounding bone tissue was filled with acrylic cement. At that time, deterioration of the cement in some cases resulted in prosthetic loosening and recurrence of pain. In many cases, a revision operation, particularly with young and active patients was required. Unfortunately, when the revision operation was performed using acrylic cement, the success rate was lower than with the initial surgery.
In response to this problem, the prosthetic implant industry began to explore the feasibility of using porous-coated prosthetic implants, especially for use with active patients. The porous-coated method involves the use of implants with sintered metal porous surfaces. By way of a non-limiting example, beaded, sintered cobalt-chrome coatings may be used on a cobalt-chrome substrate, beaded, vacuum-sintered titanium coated may be used on a titanium substrate, or vacuum-sintered titanium fiber mesh pads may be used on a titanium substrate. Additionally, truss-like structures may be used on the substrate, as well. Typically, these porous coatings would be disposed on the surfaces of the prosthetic components in direct contact with the patient""s bone tissue. For example, the stem portion of the femoral component and the outer surface of the acetabular component would be provided with these porous coatings.
Because cement is not required, these types of implants are sometimes referred to as either uncemented or cementless. As previously noted, the major difference between the porous-coated implants and the cemented implants is the metal surface of the porous-coated implants. Cemented implants typically have a smooth surface, and porous-coated implants have a rough surface resembling metal sandpaper. This porous surface allows surrounding bone tissue to grow into the pores of the porous coating, essentially making the implant a part of the patient""s body. Close contact to the bone tissue helps hold the porous surfaced implant in place until bone ingrowth has occurred.
Unfortunately, all mechanical devices, including prosthetic implants, have a tendency to generate wear particles (e.g., debris) such as particles of plastic or metallic material from the prosthetic components. In porous implants, these wear particles can migrate down into the pores of the porous coating. This may occur during loading (e.g., walking, jumping, running, and so forth) wherein the axial motion may cause xe2x80x9cpistoningxe2x80x9d of the implant. The pores may soon contain these wear particles after the implant has been installed, thus hindering new bone tissue growth into the pores of the porous implant. As a result, a condition known as osteolysis may occur. Osteolysis is generally defined as a type of particulate induced bone resorption, wherein the immune response of the patient causes the surrounding bone tissue around the implant site to resorb away from the prosthetic component. Osteolysis can lead to aseptic loosening of the implant, and eventually, implant failure.
Therefore, there exists a porous implant, and method for making same, wherein the implant has a porous coating that is capable of preventing the infiltration of wear particles into the pores, but is simultaneously capable of permitting the ingrowth of new bone tissue into the pores.
In accordance with a first embodiment of the present invention, a prosthetic implant having a porous coating on at least a portion of a surface thereof is provided, wherein the porous coating has at least one pore formed therein, wherein loading of the prosthetic implant generates at least one wear particle, wherein the prosthetic implant is adjacent to a surface comprising bone tissue, comprising a biodegradable material disposed within the at least one pore. The biodegradable material hinders infiltration of the at least one wear particle into the at least one pore and permits infiltration of the bone tissue into the at least one pore.
In accordance with a second embodiment of the present invention, a prosthetic implant is provided, wherein loading of the prosthetic implant generates at least one wear particle, wherein the prosthetic implant is adjacent to a surface comprising bone tissue, comprising a porous coating disposed on at least a portion of a surface of the prosthetic implant, wherein the porous coating has at least one pore formed therein. A biodegradable material is disposed within the at least one pore. The biodegradable material hinders infiltration of the at least one wear particle into the at least one pore and permits infiltration of the bone tissue into the at least one pore.
In accordance with a third embodiment of the present invention, a prosthetic implant is provided, wherein loading of the prosthetic implant generates at least one wear particle, wherein the prosthetic implant is adjacent to a surface comprising bone tissue, comprising a substrate, a porous coating disposed on at least a portion of a surface of the substrate, wherein the porous coating has at least one pore formed therein, and a biodegradable material disposed within the at least one pore. The biodegradable material hinders infiltration of the at least one wear particle into the at least one pore and permits infiltration of the bone tissue into the at least one pore.
In accordance with a fourth embodiment of the present invention, a method of making a prosthetic implant having a porous coating on at least a portion of a surface thereof is provided, wherein the porous coating has at least one pore formed therein, wherein loading of the prosthetic implant generates at least one wear particle, wherein the prosthetic implant is adjacent to a surface comprising bone tissue, comprising disposing a biodegradable material within the at least one pore. The biodegradable material hinders infiltration of the at least one wear particle into the at least one pore and permits infiltration of the bone tissue into the at least one pore.
In accordance with a fifth embodiment of the present invention, a method of making a prosthetic implant is provided, wherein loading of the prosthetic implant generates at least one wear particle, wherein the prosthetic implant is adjacent to a surface comprising bone tissue, comprising disposing a porous coating on at least a portion of a surface of the prosthetic implant, wherein the porous coating has at least one pore formed therein, and disposing a biodegradable material within the at least one pore. The biodegradable material hinders infiltration of the at least one wear particle into the at least one pore and permits infiltration of the bone tissue into the at least one pore.
In accordance with a sixth embodiment of the present invention, a method of making a prosthetic implant is provided, wherein loading of the prosthetic implant generates at least one wear particle, wherein the prosthetic implant is adjacent to a surface comprising bone tissue, comprising providing a substrate, disposing a porous coating on at least a portion of a surface of the substrate, wherein the porous coating has at least one pore formed therein, and disposing a biodegradable material within the at least one pore. The biodegradable material hinders infiltration of the at least one wear particle into the at least one pore and permits infiltration of the bone tissue into the at least one pore.
A more complete appreciation of the present invention and its scope can be obtained from the following detailed description of the invention and the appended claims.